ABSTRACT / PROJECT SUMMARY Medication treatment for opioid use disorder is an important component of efforts to reduce the high social costs of prescription and non-prescription opioid abuse and mortality. This approach incorporates pharmacotherapies (e.g., buprenorphine, methadone, naltrexone) as part of treatment for opioid dependence. Buprenorphine?s effectiveness has been established in numerous studies and can be prescribed in office-based settings; thus, buprenorphine is particularly important to the expansion of access to medication treatment for opioid use disorder. However, the need for treatment dramatically outstrips the number of providers authorized to prescribe it, with particularly severe shortages of providers in rural areas. Many U.S. counties do not have a single provider. In response to the shortage of buprenorphine prescribers, two federal workforce policies were established in 2016: (1) allowing nurse practitioners and physician assistants to become authorized to prescribe buprenorphine in office-based settings, and (2) increasing the maximum number of patients that can be prescribed buprenorphine by a physician from 100 to 275. Legislation passed in 2018 allows other advanced practice nurses (nurse-midwives, clinical nurse specialists, and nurse-anesthetists) to prescribe buprenorphine as well. These policies are expected to increase access to medication treatment for opioid use disorder for thousands of individuals. However, the degree to which these policies achieve their goal will depend on other environmental and policy factors, most importantly state laws that regulate advanced practice clinicians? medication prescribing. The proposed study will assess the impacts of these workforce policies on the supply and geographic reach of opioid treatment providers, with a focus on whether and how state policies facilitate or impede growth in available prescribers. The specific aims are: Aim 1: To measure the degree to which federal policies established in 2016 and 2018 impact the number and geographic distribution of clinicians with buprenorphine waivers. Aim 2: To determine whether state-level scope of practice regulations persistently moderate the effectiveness of federal policies aimed at increasing access to buprenorphine treatment. Aim 3: To assess whether expansions of the number and types of clinicians authorized to prescribe buprenorphine are associated with greater dispensing of buprenorphine. Data from multiple sources from 2016 through 2022 will be analyzed using econometric approaches that address state variation in regulations that may affect the growth of buprenorphine prescribers and utilization while controlling for other regulations and programs that might affect policy implementation. Findings from this research could be used to promote the harmonization of state and federal efforts to address the opioid crisis across the U.S. and in highly-impacted regions.